Abstract

Background: Assessing vitamin A status in populations remains a high public health priority for low- and middle-income countries. However, analytical difficulties with serum retinol measurements persist in international laboratories. Nearly all participants in a Centers for Disease Control and Prevention external quality assessment program use HPLC to measure serum retinol, but round-to-round results failing to meet acceptable criteria suggest the need to provide a straightforward stable HPLC ultraviolet (UV) method that can be adopted by these laboratories to improve performance. We present a protein precipitation HPLC-UV method that measures serum retinol below the deficiency cutoff value (<0.7 μmol/L or 20 μg/dL) that is suitable for low- and middle-income countries and uses commercially available materials.

Results: With only 25 μL of serum, the limit of detection was 0.52 μg/dL. Single- and multipoint calibration generated equivalent results. Over several years, between-run imprecision was ≤7.1% in multiple quality-control materials. Overall mean (CV) method bias for NIST-certified reference materials (e-series) was −0.2% (5.8%). Maximally, 180 samples were processed within 24 h.

Conclusions: This method was robust and stable over years and accurately measured serum retinol with low-volume samples. Thus, it may be of interest to low- and middle-income countries and to pediatric and finger stick applications.

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